Methods for the Diagnosis and Treatment of Neurological and Neurodegenerative Diseases, Disorders and Associated Processes

ABSTRACT

The invention generally relates to methods for the diagnosis and treatment of neurological and neurodegenerative diseases, disorders, and associated processes. Specifically, the present invention is directed toward methods to determine prognosis, diagnosis or efficacy of a therapeutic regimen by using a detectable label to measure levels of alpha-synuclein.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 14/345,390 filed Mar. 17, 2014, which claims the benefit under 35USC §371 National Stage application of International Application No.PCT/US12/56144 filed Sep. 19, 2012; which claims the benefit under 35USC §119(e) to U.S. Application Ser. No. 61/536,300 filed Sep. 19, 2011.The disclosure of each of the prior applications is considered part ofand is incorporated by reference in the disclosure of this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention generally relates to methods for the diagnosis andtreatment of neurological and neurodegenerative diseases, disorders, andassociated processes, and more specifically, to levels of alphasynuclein and correlation with disease.

2. Background Information

The protein alpha-synuclein has been implicated in Parkinson's Disease(PD) through a variety of human and animal studies. Recent studies haveshown that the CSF concentration of alpha-synuclein is significantlylower in patients with PD than in control subjects, suggesting that themetabolism of alpha-synuclein is altered in patients with PD. Like otherprotein misfolding diseases, protein misfolding isconcentration-dependent. Thus, decreasing synthesis or increasingclearance of synuclein is a potential way to develop treatments for PDand drug companies have focused on the metabolism of this protein as adrug target.

The stable isotope labeling kinetic (SILK) assay relies on the abilityto detect metabolic incorporation of stable isotope labeled amino acidsinto proteins and peptides. Stable isotopes add a small amount of weight(2-100 Daltons) to peptides containing the stable isotope and thisadditional weight can be measured by a mass spectrometer. By measuringmetabolic incorporation of stable isotopes into proteins in the CSF atvarious times after administration of a stable isotope, the SILK assaycan be used to measure production and clearance of proteins in the humancentral nervous system.

The following describes the protocol for measuring the metabolism ofbrain derived alpha-synuclein in a human subject. A study participant isidentified and enrolled in the study. On the first day of the study theparticipant will have IV and lumbar catheters placed and will beadministered a stable isotope for a pre-determined amount of time.Samples of plasma and CSF will be drawn through the catheters atpre-determined times. Alpha-synuclein will then be isolated from thebiological samples and the incorporation of the stable isotope into theprotein will be measured by a mass spectrometer. The change in labeledto unlabeled alpha-synuclein over time will allow for calculation ofproduction and clearance rates for the protein.

Measuring alpha-synuclein metabolism can provide results to inform aboutsynthesis and clearance rates of alpha-synuclein in normal as well asdisease states, as well as provide a method to directly determine theeffects in humans of treatments which target alpha-synuclein synthesisand clearance.

SUMMARY OF THE INVENTION

In one embodiment of the invention, we describe the methods by whichalpha-synuclein is isolated from biological samples byimmunoprecipitation using an antibody that recognizes alpha-synuclein.In this embodiment, the isolated protein is eluted from the antibody,for example by using formic acid and then digested with trypsin oranother protease. Incorporation of stable isotopes into alpha-synucleinpeptides is then analyzed on a mass spectrometer and a ratio of labeledto unlabeled alpha-synuclein is calculated.

In one embodiment, the present invention is a method to determineprognosis, diagnosis or efficacy of a therapeutic regimen in a subjectcomprising contacting a biological sample from a subject with adetectable isotope to detect the level of alpha-synuclein in the sample.

In an embodiment, the present invention is a method to diagnose analpha-synuclein related disease or disorder comprising: (a)administration of a labeled moiety to a subject suspected of having analpha-synuclein related disease or disorder; (b) collection of abiological sample from the subject and a corresponding normal sample;(c) measurement of labeled alpha-synuclein and unlabeled alpha-synucleinfrom the subject and corresponding normal sample; (d) determination ofthe ratio of labeled alpha-synuclein to unlabeled alpha-synuclein fromthe subject and corresponding normal sample; (e) determination ofalpha-synuclein metabolism from the ratios of step (d); and (f)comparison of the alpha-synuclein metabolism from the subject to thealpha-synuclein metabolism from the corresponding normal sample, whereina change in the alpha-synuclein metabolism of the subject compared tothe corresponding normal sample is indicative of positive diagnosis ofan alpha-synuclein related disease or disorder, thereby diagnosing analpha-synuclein related disease or disorder.

In another embodiment, the present invention is a method to determinethe prognosis an alpha-synuclein related disease or disorder comprising:(a) administration of a labeled moiety to a subject suspected of havingan alpha-synuclein related disease or disorder; (b) collection of abiological sample from the subject and a corresponding normal sample;(c) measurement of labeled alpha-synuclein and unlabeled alpha-synucleinfrom the subject and corresponding normal sample; (d) determination ofthe ratio of labeled alpha-synuclein to unlabeled alpha-synuclein fromthe subject and corresponding normal sample; (e) determination ofalpha-synuclein metabolism from the ratios of step (d); and (f)comparison of the alpha-synuclein metabolism from the subject to thealpha-synuclein metabolism from the corresponding normal sample, whereina change in the alpha-synuclein metabolism of the subject compared tothe corresponding normal sample is indicative of positive prognosis ofan alpha-synuclein related disease or disorder, thereby prognosing analpha-synuclein related disease or disorder.

In an additional embodiment, the present invention is a method todetermine the efficacy of a therapeutic regimen to treat analpha-synuclein related disease or disorder comprising: (a)administration of a labeled moiety and a therapeutic agent to a subjectsuspected of having an alpha-synuclein related disease or disorder; (b)collection of a biological sample from the subject and a correspondingnormal sample; (c) measurement of labeled alpha-synuclein and unlabeledalpha-synuclein from the subject and corresponding normal sample; (d)determination of the ratio of labeled alpha-synuclein to unlabeledalpha-synuclein from the subject and corresponding normal sample; and(e) determination of alpha-synuclein metabolism from the ratios of step(d); (f) comparison of the alpha-synuclein metabolism from the subjectto the alpha-synuclein metabolism from the corresponding normal sample,wherein a change in the alpha-synuclein metabolism of the subjectcompared to the corresponding normal sample is indicative of efficacy ofa therapeutic regimen of a therapeutic agent to treat an alpha-synucleinrelated disease or disorder, thereby determining the efficacy of atherapeutic regimen to treat an alpha-synuclein related disease ordisorder.

In an embodiment, the present invention is an in vivo method to identifya therapeutic agent to treat an alpha-synuclein related disease ordisorder comprising: (a) administration of a labeled moiety and atherapeutic agent to a subject suspected of having an alpha-synucleinrelated disease or disorder; (b) collection of a biological sample fromthe subject and a corresponding normal sample; (c) measurement oflabeled alpha-synuclein and unlabeled alpha-synuclein from the subjectand corresponding normal sample; (d) determination of the ratio oflabeled alpha-synuclein to unlabeled alpha-synuclein from the subjectand corresponding normal sample; (e) determination of alpha-synucleinmetabolism from the ratios of step (d); and (f) comparison of thealpha-synuclein metabolism from the subject to the alpha-synucleinmetabolism from the corresponding normal sample, wherein a change inalpha-synuclein metabolism of the subject compared to the correspondingnormal sample is indicative of the identification of a therapeutic agentto treat an alpha-synuclein related disease or disorder, therebyidentifying a therapeutic agent to treat an alpha-synuclein relateddisease or disorder.

In one embodiment, the present invention is an in vitro method toidentify a therapeutic agent to treat an alpha-synuclein related diseaseor disorder comprising: (a) administration of a labeled moiety and atherapeutic agent to cells; (b) collection of alpha-synuclein from thecells and a corresponding normal sample; (c) measurement of labeledalpha-synuclein and unlabeled alpha-synuclein from the cells andcorresponding normal sample; (d) determination of the ratio of labeledalpha-synuclein to unlabeled alpha-synuclein from the cells andcorresponding normal sample; (e) determination of alpha-synucleinmetabolism from the ratios of step (d); and (f) comparison of thealpha-synuclein metabolism from the cells to the alpha-synucleinmetabolism from the corresponding normal sample, wherein a change inalpha-synuclein metabolism of the cells compared to the correspondingnormal sample is indicative of the identification of a therapeutic agentto treat an alpha-synuclein related disease or disorder, therebyidentifying a therapeutic agent to treat an alpha-synuclein relateddisease or disorder an alpha-synuclein related disease or disorder.

In one embodiment, the present invention is a method to predict subjectresponse to a therapeutic agent to treat an alpha-synuclein relateddisease or disorder comprising: (a) administration of a labeled moietyand a therapeutic agent to a subject suspected of having analpha-synuclein related disease or disorder; (b) collection of abiological sample from the subject and a corresponding normal sample;(c) measurement of labeled alpha-synuclein and unlabeled alpha-synucleinfrom the subject and corresponding normal sample; (d) determination ofthe ratio of labeled alpha-synuclein to unlabeled alpha-synuclein fromthe subject and corresponding normal sample; (e) determination ofalpha-synuclein metabolism from the ratios of step (d); and (f)comparison of the alpha-synuclein metabolism from the subject to thealpha-synuclein metabolism from the corresponding normal sample, whereina change in the alpha-synuclein metabolism of the subject compared tothe corresponding normal sample is indicative of the identification of atherapeutic agent to treat an alpha-synuclein related disease ordisorder, thereby diagnosing an alpha-synuclein related disease ordisorder.

In one aspect, the labeled moiety is a labeled amino acid. In a furtheraspect, the amino acid is labeled with a radioisotope or a non-radiolabeled isotope. In one aspect, the amino acid is labeled with anon-radio labeled isotope. In an additional aspect, the non-radiolabeled isotope can be ²H, ¹³C, ¹⁵N, ¹⁷ or ¹⁸O and ^(33, 34 or 36)S. Ina further aspect, the amino acid can be leucine, isoleucine andphenylalanine. Further, the labeled amino acid maybe one or more of¹⁵N_(x) labeled leucine, wherein x=1-6; ¹³C_(x) labeled phenylalanine,wherein x=1-9 and ¹³C_(x) labeled isoleucine, wherein x=1-6. In oneaspect, the labeled moiety is labeled water. In a further aspect, thelabeled water is deuterated water (²H₂O), oxygen 18 water (H₂ ¹⁸O) orother similar molecules. In one aspect, the biological sample is abodily fluid or a tissue sample. In a further aspect, the bodily fluidcan be blood, plasma, blood serum, cerebral spinal fluid (CSF), urine,saliva, perspiration and tears. In one aspect, the bodily fluid is CSF.In an additional aspect, the tissue sample is a CNS sample. In a furtheraspect, the CNS sample can be tissue from the CNS system, brain tissue,the forebrain tissue, the interbrain tissue, the midbrain tissue, thehindbrain tissue and the spinal cord tissue.

In one aspect the therapeutic agent can be small molecule inhibitors ofalpha-synuclein, antibodies against alpha-synuclein, alpha-synucleinclearance activators, sirtuin 2 inhibitors, proteomsome inhibitors,small molecule inhibitors of alpha-synuclein polymerization, L-DOPA,cholesterylester transfer protein (CEPT) inhibitors, metalloproteaseinhibitors, cholinesterase inhibitors, NMDA receptor antagonists,hormones, neuroprotective agents and cell death inhibitors. In oneaspect, the therapeutic agent is L-DOPA.

In one embodiment, the present invention is a kit for determineprognosis, diagnosis or efficacy of a therapeutic regimen in a subjecthaving or suspected of having an alpha-synuclein related disease ordisorder. In one aspect, the kit comprises one or more labeled moietiesand a means for administering the one or more moieties to a subject. Inan additional aspect, the kit further comprises a means for obtaining abiological sample and instructions for determining the ratio of labeledto unlabeled alpha-synuclein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the amino acid sequence of alpha-synuclein (SEQ ID NO:1)showing the tryptic cleavage sites.

FIG. 2 shows a multiple sequence comparison (SEQ ID NOs:1-3) showingdifferences in the amino acid sequence of alpha-, beta- andgamma-synuclein.

FIG. 3 shows tryptic peptides originating from alpha-synuclein (SEQ IDNOs:4-13) observed on the mass spectrometer. We have analyzedalpha-synuclein isolated from biological sources such as cerebrospinalfluid, conditioned cell culture media, and cell lysates as well asrecombinant alpha-synuclein.

FIG. 4 shows the mass spectrum of alpha-synuclein 81-96 peptide (SEQ IDNO:13). Contains essential amino acid phenylalanine (F). The presence ofa phenylalanine in the 81-96 tryptic peptide makes this peptide apeptide that can be used to monitor metabolism of alpha-synuclein byadministration of stable isotope labeled phenylalanine.

FIG. 5 shows the mass spectrum of alpha-synuclein 33-43 peptide (SEQ IDNO:6). Contains essential amino acid leucine (L). The presence of aleucine in the 33-43 tryptic peptide makes this peptide a peptide thatcan be used to monitor metabolism of alpha-synuclein by administrationof stable isotope labeled leucine.

FIG. 6 shows the mass spectrum of alpha-synuclein 35-43 peptide (SEQ IDNO:7). Contains essential amino acid leucine (L). The presence of aleucine in the 35-43 tryptic peptide makes this peptide a peptide thatcan be used to monitor metabolism of alpha-synuclein by administrationof stable isotope labeled leucine.

FIG. 7 shows alpha-synuclein standard curves derived from samples taken3, 5 and 7 days after administration of the labeled moiety.

FIG. 8 shows the relative intensity of alpha-synuclein ions derived fromsamples taken 3, 5 and 7 days after administration of the labeledmoiety.

FIG. 9 shows the relative ion intensity of alpha-synuclein measured inlabeled and unlabeled samples.

FIG. 10 shows the levels of amyloid beta protein and alpha-synucleindetected by the SILK assay over 36 hours post administration of thelabeled moiety.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is based, in part, on the discovery that stableisotope labeling of biomolecules leads to small differences in molecularweight of the biomolecules, but does not alter the physical or chemicalproperties of the biomolecules. Using the techniques provided herein,analysis of biomolecules can be used to diagnose and/or treat a subjecthaving or at risk of developing a neurological or neurodegenerativedisorder. Accordingly, the present invention provides methods and kitsuseful for measuring the metabolism of alpha-synuclein in a subject.

The invention also provides a method to assess whether a therapeuticagent affects the production or clearance rate of alpha-synuclein in thesubject. Accordingly, the method may be used to determine the optimaldoses and/or optimal dosing regimens of the therapeutic agent.Additionally, the method may be used to determine which subjects respondbetter to a particular therapeutic agent. For example, subjects withincreased production of alpha-synuclein may respond better to onetherapeutic agent, whereas subjects with decreased clearance ofalpha-synuclein may respond better to another therapeutic agent.Alternatively, subjects with one particular genotype may respond betterto a particular therapeutic agent than those with a different genotype.Finally, by allowing isoform specific quantitation, the method may beused to determine whether a therapeutic agent can modulate theproduction of an alpha-synuclein by switching production of one isoformto another isoform.

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural references unless the contextclearly dictates otherwise. Thus, for example, references to “themethod” includes one or more methods, and/or steps of the type describedherein which will become apparent to those persons skilled in the artupon reading this disclosure and so forth.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although any methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of the invention, the preferred methods andmaterials are now described.

The term “subject” as used herein refers to any individual or patient towhich the subject methods are performed. Generally the subject is human,although as will be appreciated by those in the art, the subject may bean animal. Thus other animals, including mammals such as rodents(including mice, rats, hamsters and guinea pigs), cats, dogs, rabbits,farm animals including cows, horses, goats, sheep, pigs, etc., andprimates (including monkeys, chimpanzees, orangutans and gorillas) areincluded within the definition of subject. In addition, the term“subject” may refer to a culture of cells, where the methods of theinvention are performed in vitro to assess, for example, efficacy of atherapeutic agent.

As used herein, the terms “sample” and “biological sample” refer to anysample suitable for the methods provided by the present invention. Asample of cells used in the present method can be obtained from tissuesamples or bodily fluid from a subject, or tissue obtained by a biopsyprocedure (e.g., a needle biopsy) or a surgical procedure. In certainembodiments, the biological sample of the present invention is a sampleof bodily fluid, e.g., cerebral spinal fluid (CSF), blood, plasma,urine, saliva, and tears.

The term “antibody” as used in this invention is meant to include intactmolecules of polyclonal or monoclonal antibodies, as well as fragmentsthereof, such as Fab and F(ab′)₂, Fv and SCA fragments which are capableof binding an epitopic determinant. The term “specifically binds” or“specifically interacts,” when used in reference to an antibody meansthat an interaction of the antibody and a particular epitope has adissociation constant of at least about 1×10⁻⁶, generally at least about1×10⁻⁷, usually at least about 1×10⁻⁸, and particularly at least about1×10⁻⁹ or 1×10⁻¹⁰ or less.

As used herein the term “alpha-synuclein related disease or disorder”refers to any disease or disorder in which circulating levels orproduction of alpha-synuclein or alpha-synuclein metabolism is changedfrom normal. This change can be an increase or decrease inalpha-synuclein levels or metabolism compared to normal.

As disclosed herein, stable isotope labeling of alpha-synuclein leads tosmall differences in molecular weight of alpha-synuclein, but does notalter the general physical or chemical properties of alpha-synuclein.Thus, alpha-synuclein will bind to antibodies and elute off a liquidchromatography column in an identical fashion. Only sensitiveinstruments, such as mass spectrometers, provide the ability to measurethe small differences in weight between labeled and unlabeledalpha-synuclein.

Several different moieties may be used to label alpha-synuclein.Generally speaking, the two types of labeling moieties utilized in themethod of the invention are radioactive isotopes and non-radioactive(stable) isotopes. In one embodiment, non-radioactive isotopes may beused and measured by mass spectrometry. Preferred stable isotopesinclude deuterium (²H), ¹³C, ¹⁵N, _(17 or 18)O, and _(33, 34, or 36)S,but it is recognized that a number of other stable isotopes that changethe mass of an atom by more or less neutrons than is seen in theprevalent native form would also be effective. A suitable labelgenerally will change the mass of alpha-synuclein such that it can bedetected in a mass spectrometer. Alternatively, a radioactive isotopemay be used, and the labeled alpha-synuclein may be measured with ascintillation counter (or via nuclear scintigraphy) as well as by a massspectrometer. One or more labeled moieties may be used simultaneously orin sequence.

Thus, in one embodiment, when the method is employed to measure themetabolism of alpha-synuclein, the labeled moiety typically will be anamino acid. Those of skill in the art will appreciate that several aminoacids may be used to provide the label of alpha-synuclein. Generally,the choice of amino acid is based on a variety of factors such as: (1)The amino acid generally is present in at least one residue ofalpha-synuclein. (2) The amino acid is generally able to quickly reachthe site of protein production and rapidly equilibrate across theblood-brain barrier or other tissue or cellular barriers. (3) The aminoacid label generally does not influence the metabolism of the protein ofinterest (e.g., very large doses of leucine may affect musclemetabolism). And (4) availability of the desired amino acid (i.e., someamino acids are much more expensive or harder to manufacture thanothers).

In one embodiment, the amino acid is an essential amino acid (notproduced by the body), so that a higher percent of labeling may beachieved. In another embodiment, the amino acid is a non-essential aminoacid. Exemplary amino acids include, but are not limited to, leucine,isoleucine, and phenylalanine. As such, in one embodiment, the labeledamino acid is one or more of a ¹⁵N-labeled amino acid, a ¹³C_(x)-labeledphenylalanine, where x=1 to 9, a ¹³C_(x)-labeled isoleucine, where x=1to 6. For example, ¹³C₆-phenylalanine, which contains six ¹³C atoms, maybe used to label alpha-synuclein. In another embodiment, ¹³C₆-leucinemay be used to label alpha-synuclein.

There are numerous commercial sources of labeled amino acids, bothnon-radioactive isotopes and radioactive isotopes. Generally, thelabeled amino acids may be produced either biologically orsynthetically. Biologically produced amino acids may be obtained from anorganism (e.g., kelp/seaweed) grown in an enriched mixture of ¹³C, ¹⁵N,or another isotope that is incorporated into amino acids as the organismproduces proteins. The amino acids are then separated and purified.Alternatively, amino acids may be made with known synthetic chemicalprocesses.

In one embodiment, when the method is employed to measure the metabolismof alpha-synuclein, the labeled moiety typically will be labeled water.In one aspect the labeled water is deuterated water (²H₂O). In anotheraspect, the labeled water is oxygen 18 water (H₂ ¹⁸O). In a furtheraspect, the labeled water is a molecule similar to deuterated water oroxygen 18 water.

The labeled moiety (e.g., labeled amino acid) may be administered to asubject by several methods. Suitable routes of administration includeintravenously, intra-arterially, subcutaneously, intraperitoneally,intramuscularly, or orally. In one embodiment, the labeled moiety may beadministered by intravenous infusion. In another embodiment, the labeledmoiety may be orally ingested.

The labeled moiety may be administered slowly over a period of time, asa large single dose depending upon the type of analysis chosen (e.g.,steady state or bolus/chase), or slowly over a period of time after aninitial bolus dose. To achieve steady-state levels of the labeledalpha-synuclein, the labeling time generally should be of sufficientduration so that the labeled alpha-synuclein may be reliably quantified.In one embodiment, the labeled moiety is administered as a single oraldose. In another embodiment, the labeled moiety is administered for aperiod of time ranging from about one hour to about 36 hours. In anotherembodiment, the labeled moiety is administered for a period of timeranging from about 6 hours to about 12 hours. In yet another embodiment,the labeled moiety is administered for a period of time ranging fromabout 9 hours to about 12 hours. In yet another embodiment, the labeledmoiety is administered for a period of time ranging from about 9 hoursto about 24 hours. The rate of administration of the labeled moiety mayrange from about 0.5 mg/kg/hr to about 5 mg/kg/hr. In one embodiment,the rate of administration of labeled leucine is from about 1 mg/kg/hrto about 3 mg/kg/hr. In another embodiment, the rate of administrationof labeled leucine is from 1.8 mg/kg/hr to about 2.5 mg/kg/hr. Inanother embodiment, the labeled leucine may be administered as a bolusof between about 50 and about 500 mg/kg body weight of the subject,between about 50 and about 300 mg/kg body weight of the subject, orbetween about 100 and about 300 mg/kg body weight of the subject. In yetanother embodiment, the labeled leucine may be administered as a bolusof about 200 mg/kg body weight of the subject. In an alternateembodiment, the labeled leucine may be administered intravenously asdetailed above after an initial bolus of between about 0.5 to about 10mg/kg, between about 1 to about 4 mg/kg, or about 2 mg/kg body weight ofthe subject. In another embodiment the water will be administered dailyover 1-7 days.

Those of skill in the art will appreciate that the amount (or dose) ofthe labeled moiety can and will vary. Generally, the amount is dependenton (and estimated by) the following factors: (1) The type of analysisdesired. For example, to achieve a steady state of about 15% labeledleucine in plasma requires about 2 mg/kg/hr over about 9 hr after aninitial bolus of 3 mg/kg over 10 min. In contrast, if no steady state isrequired, a large bolus of labeled moiety (e.g., 1 or 5 grams of labeledleucine) may be given initially. (2) The rate of metabolism ofalpha-synuclein. For example, if alpha-synuclein is being producedrapidly, then less labeling time may be needed and less label may beneeded—perhaps as little as 0.5 mg/kg over 1 hour. However, mostproteins have half-lives of hours to days and, so more likely, acontinuous infusion for 9, 12 or 24 hours may be used at 0.5 mg/kg to 4mg/kg. And (3) the sensitivity of detection of the label. For example,as the sensitivity of label detection increases, the amount of labelthat is needed may decrease.

It should be understood that more than one labeled moiety may be used ina single subject. This would allow multiple labeling of alpha-synucleinand may provide information on the production or clearance ofalpha-synuclein at different times. For example, a first label may begiven to subject over an initial time period, followed by apharmacologic agent (drug), and then a second label may be administered.In general, analysis of the samples obtained from the subject wouldprovide a measurement of metabolism of alpha-synuclein before AND afterdrug administration, directly measuring the pharmacodynamic effect ofthe drug in the same subject. Alternatively, multiple labels may be usedat the same time to increase labeling of alpha-synuclein.

The method of the invention provides that a sample be obtained from thesubject such that the metabolism of alpha-synuclein can be determined.In one embodiment, the sample is a body fluid. Suitable body fluidsinclude, but are not limited to, cerebral spinal fluid (CSF), bloodplasma, blood serum, urine, saliva, perspiration, and tears. In anotherembodiment, the sample is a tissue sample, such as a sample of tissuefrom the central nervous system (CNS). The sample generally will becollected using standard procedures well known to those of skill in theart.

In one embodiment, the sample is a CNS sample, which includes, but isnot limited to, tissue from the central nervous system, which comprisesbrain tissue and spinal cord tissue. In one embodiment of the invention,the CNS sample may be taken from brain tissue, including, but notlimited to, tissue from the forebrain (e.g., cerebral cortex, basalganglia, hippocampus), the interbrain (e.g., thalamus, hypothalamus,subthalamus), the midbrain (e.g., tectum, tegmentum), or the hindbrain(e.g., pons, cerebellum, medulla oblongata). In another embodiment, theCNS sample may be collected from spinal cord tissue. In still otherembodiments, CNS samples from more than one CNS region may be taken.Accordingly, the metabolism of alpha-synuclein may be measured indifferent CNS samples, e.g., in the cortex and the hippocampus,simultaneously.

CNS samples may be obtained by known techniques. For instance, braintissue or spinal cord tissue may be obtained via dissection orresection. Alternatively, CNS samples may be obtained using lasermicrodissection. The subject may or may not have to be sacrificed toobtain the sample, depending on the CNS sample desired and the subjectutilized.

In one embodiment, the sample is obtained from the subject at a singlepredetermined time point, for example, within an hour of labeling. Ingeneral, for proteins with fast metabolism, samples obtained during thefirst 12-18 hours after the start of administration of the labeledmoiety may be used to determine the rate of production ofalpha-synuclein, and samples taken during 24-36 hrs after the start ofadministration of the labeled moiety may be used to determine theclearance rate of alpha-synuclein. In general, for proteins with slowmetabolism, samples obtained during the first 1-4 days after the startof administration of the labeled moiety may be used to determine therate of production of alpha-synuclein, and samples taken during 4-14days after the start of administration of the labeled moiety may be usedto determine the clearance rate of alpha-synuclein. In anotherembodiment, the sample is obtained from the subject hourly from 0 to 12hours, 0 to 24 hours, or 0 to 36 hours. In yet another embodiment,samples may be taken from an hour to days or even weeks apart dependingupon the production and clearance rates of alpha-synuclein.

Those of skill in the art will appreciate that the labeled moiety shouldbe administered in a timely fashion which will allow observation ofincorporation of the labeled moiety into alpha-synuclein. The labelingof alpha-synuclein will take place as the protein is synthesized insidethe cell. But the incorporation of the label into alpha-synuclein isonly measured once the protein has exited the cell and entered thecerebrospinal fluid or the blood stream. If the protein undergoescomplex processing in order to exit the cell, the time from synthesisuntil appearance in the bodily fluid could be significant. Thus if ittakes 24-48 hours for alpha-synuclein to show up in CSF, administrationof label may have to occur 24-48 hours before the start of CSF sampling.Alternatively, if it takes 48-72 hours for alpha-synuclein to show up inCSF, administration of label may have to occur 48-72 hours before thestart of CSF sampling. Further, if it takes 3 days to one week foralpha-synuclein to show up in CSF, administration of label may have tooccur 3 days to one week before the start of CSF sampling.

It should be understood that if samples at different time-points aredesired, more than one subject may be used. For instance, one subjectmay be used for a baseline sample, another subject for a time-point ofone hour post administration of the labeled moiety, another subject fora time-point six hours post administration of the labeled moiety.

Accordingly, the present invention provides that detection of the amountof labeled alpha-synuclein and the amount of unlabeled alpha-synucleinin the sample may be used to determine the ratio of labeledalpha-synuclein to unlabeled alpha-synuclein, which in turn, may be usedto estimate the production and clearance rates of alpha-synuclein in thesubject. Exemplary means for detecting differences in mass between thelabeled and unlabeled alpha-synuclein include, but are not limited to,liquid chromatography mass spectrometry, gas chromatography massspectrometry, MALDI-TOF mass spectrometry, and tandem mass spectrometry.

However, prior to detecting the ratio of labeled alpha-synuclein tounlabeled alpha-synuclein, it may be desirable to isolate and/orseparate alpha-synuclein from other biomolecules in the sample. Thus, inone embodiment, immunoprecipitation may be used to isolate and purifyalpha-synuclein before it is analyzed. In another embodiment,alpha-synuclein may be isolated or purified by affinity chromatographyor immunoaffinity chromatography. Alternatively, mass spectrometershaving chromatography setups may be used to separate biomoleculeswithout immunoprecipitation, and then alpha-synuclein may be measureddirectly. In an exemplary embodiment, alpha-synuclein may beimmunoprecipitated and then analyzed by a liquid chromatography systeminterfaced with a tandem MS unit equipped with an electrosprayionization source (LC-ESI-tandem MS).

In another aspect, the invention provides that the metabolism ofmultiple biomolecules in the same sample may be measured simultaneously.That is, both the amount of unlabeled and labeled biomolecule may bedetected and measured separately or at the same time for multiplebiomolecules. As such, the invention provides a useful method forscreening changes in production and clearance of one or morebiomolecules on a large scale (i.e., proteomics/metabolomics) andprovides a sensitive means to detect and measure biomolecules involvedin the underlying pathophysiology. In one aspect, the invention alsoprovides a means to measure multiple types of biomolecules. In thiscontext, for example, a protein and a lipid may be measuredsimultaneously or sequentially. For example, both alpha-synuclein and Aβcould be isolated from a CSF sample and the production and clearance ofthe two individual proteins be determined in the same subject.

Once the amount of labeled and unlabeled alpha-synuclein has beendetected in a sample, the ratio or percent of labeled alpha-synuclein tounlabeled alpha-synuclein may be determined by dividing the amount oflabeled alpha-synuclein with the amount of unlabeled alpha-synuclein. Ifa mass spectrometer is used for detection of alpha-synuclein, the ratiowould be calculated by dividing the ion intensity of labeledalpha-synuclein with the ion intensity of unlabeled alpha-synuclein.

The invention allows measurement of the labeled and unlabeled protein atthe same time, so that the ratio of labeled to unlabeled protein, aswell as other calculations, may be made. As measurements of labelingratios are combined over different sampling times after infusion of thestable isotope, the data can be combined to form a metabolic profile.Those of skill in the art will be familiar with the first order kineticmodels of labeling that may be used with the method of the invention.For example, the fractional synthesis rate (FSR) may be calculated. TheFSR equals the initial rate of increase of labeled to unlabeled proteindivided by the precursor enrichment. Likewise, the fractional clearancerate (FCR) may be calculated. In addition, other parameters, such asfractional turnover rate (FTR), lag time, and isotopic tracer steadystate, may be determined and used as measurements of the protein'smetabolism and physiology. Also, modeling may be performed on the datato fit multiple compartment models to estimate transfer betweencompartments. Of course, the type of mathematical modeling chosen willdepend on the individual synthesis and clearance parameters (e.g.,one-pool, multiple pools, steady state, non-steady-state, compartmentalmodeling, etc.). As used herein, “steady state” refers to a state duringwhich there is insignificant change in the measured parameter over aspecified period of time.

Stable isotope kinetic labeling (SILK) methodology has been shown todetect metabolic incorporation of stable (non-radioactive) isotopes intonewly synthesized proteins in the cerebrospinal fluid of living subject.For detailed information regarding SILK, see U.S. Pub. Nos. 2008/0145941and 2009/0142766, and International PCT Pub. No. WO 2006/107814, theentire content of each of which is incorporated herein by reference).SILK makes it possible to measure the production and clearance rates ofproteins in the central nervous system. Thus far, this methodology hasbeen applied to measuring the production and clearance of the amyloidbeta protein (Aβ) implicated in Alzheimer's disease (AD).

However, until now, the current version of the SILK assay measures onlythe metabolism of Aβ. In the data demonstrated here we show that theSILK method can also be applied to alpha-synuclein. This assay isdistinct in the use of an antibody that specifically binds toalpha-synuclein for isolation of alpha-synuclein from the biologicalfluid and in the selection of alpha-synuclein specific peptides formonitoring of stable isotope incorporation into alpha-synuclein.

Accordingly, the production of protein is typically based upon the rateof increase of the labeled/unlabeled protein ratio over time (i.e., theslope, the exponential fit curve, or a compartmental model fit definesthe rate of protein production). For these calculations, a minimum ofone sample is typically required (one could estimate the baselinelabel), two are preferred, and multiple samples are more preferred tocalculate an accurate curve of the uptake of the label into the protein(i.e., the production rate). If multiple samples are used or preferred,the samples need not be taken from the same subject. For instance,proteins may be labeled in five different subjects at time point zero,and then a single sample taken from each subject at a different timepoint post-labeling.

Conversely, after the administration of labeled amino acid isterminated, the rate of decrease of the ratio of labeled to unlabeledprotein typically reflects the clearance rate of that protein. For thesecalculations, a minimum of one sample is typically required (one couldestimate the baseline label), two are preferred, and multiple samplesare more preferred to calculate an accurate curve of the decrease of thelabel from the protein over time (i.e., the clearance rate). If multiplesamples are used or preferred, the samples need not be taken from thesame subject. For instance, proteins may be labeled in five differentsubjects at time point zero, and then a single sample taken from eachsubject at a different time point post-labeling. The amount of labeledprotein in a CNS sample at a given time reflects the production rate orthe clearance rate (i.e., removal or destruction) and is usuallyexpressed as percent per hour or the mass/time (e.g., mg/hr) of theprotein in the subject.

The method of the invention may be used to diagnose or monitor theprogression of a neurological or neurodegenerative disease by measuringthe in vivo metabolism of alpha-synuclein in a subject. Additionally,the methods of the invention may be used to monitor the treatment of aneurological or neurodegenerative disease by measuring the in vivometabolism of alpha-synuclein in a subject. The metabolism ofalpha-synuclein may be linked to a neurological or neurodegenerativedisease such that any increase or decrease may be indicative of thepresence or progression of the disease. Thus, the metabolism ofalpha-synuclein may be compared to the metabolism of alpha-synuclein ina corresponding normal sample, to the metabolism of alpha-synuclein in asubject of known neurological or neurodegenerative disease state, to themetabolism of alpha-synuclein from the same subject determined at anearlier time, or any combination thereof.

In addition, such methods may help identify an individual as having apredisposition for the development of the disease, or may provide ameans for detecting the disease prior to the appearance of actualclinical symptoms. A more definitive diagnosis of this type may allowhealth professionals to employ preventative measures or aggressivetreatment earlier thereby preventing the development or furtherprogression of the disease.

As used herein a “corresponding normal sample” refers to a sample fromthe same organ and/or of the same type as the sample being examined. Inone aspect, the corresponding normal sample comprises a sample of cellsobtained from a healthy individual. Such a corresponding normal samplecan, but need not be, from an individual that is age-matched and/or ofthe same sex as the individual providing the sample being examined. Inanother aspect, the corresponding normal sample comprises a sample ofcells obtained from an otherwise healthy portion of tissue of thesubject from which the sample being tested is obtained.

Reference to the metabolism of alpha-synuclein in a subject of knownneurological or neurodegenerative disease state includes a predeterminedmetabolism of alpha-synuclein linked to a neurological orneurodegenerative disease. Thus, the metabolism may be compared to aknown metabolism of alpha-synuclein obtained from a sample of a singleindividual or may be from an established cell line of the same type asthat of the subject. In one aspect, the established cell line can be oneof a panel of such cell lines, wherein the panel can include differentcell lines of the same type of disease and/or different cell lines ofdifferent diseases associated with alpha-synuclein. Such a panel of celllines can be useful, for example, to practice the present method whenonly a small number of cells can be obtained from the subject to betreated, thus providing a surrogate sample of the subject's cells, andalso can be useful to include as control samples in practicing thepresent methods.

Exemplary neurological or neurodegenerative diseases that may be linkedto the metabolism of alpha-synuclein include, but are not limited to,Alzheimer's Disease, Parkinson's Disease, stroke, frontal temporaldementias (FTD5), aging-related disorders and dementias, Lewy BodyDisease, Traumatic Brain Injury (TBI), and Amyotrophic Lateral Sclerosis(ALS or Lou Gehrig's Disease). It is also envisioned that the method ofthe invention may be used to study the normal physiology, metabolism,and function of the CNS.

In another aspect, the present invention provides a method for assessingwhether a therapeutic agent used to treat a neurological orneurodegenerative disease affects the metabolism of alpha-synuclein inthe subject. For example, the metabolism of alpha-synuclein may bemeasured to determine if a given therapeutic agent results in anincrease, or a decrease in the production or clearance ofalpha-synuclein. In one embodiment, the method is performed in vivo, asherein described. In another embodiment, the method is performed invitro utilizing a culture of cells, where the culture of cells is the“subject” in the methods described herein. Accordingly, use of themethods provided herein will allow those of skill in the art toaccurately determine the degree of change in the metabolism ofalpha-synuclein, and correlate these measurements with the clinicaloutcome of the disease modifying treatment. Results from this aspect ofthe invention, therefore, may help determine the optimal doses andfrequency of doses of a therapeutic agent, may assist in thedecision-making regarding the design of clinical trials, and mayultimately accelerate validation of effective therapeutic agents for thetreatment of neurological or neurodegenerative diseases.

Thus, the method of the invention may be used to predict which subjectswill respond to a particular therapeutic agent. For example, subjectswith increased metabolism of alpha-synuclein may respond to a particulartherapeutic agent differently than subjects with decreased metabolism ofalpha-synuclein. In particular, results from the method may be used toselect the appropriate treatment (e.g., an agent that blocks theproduction of alpha-synuclein or an agent that increases the clearancealpha-synuclein) for a particular subject. Similarly, results from themethod may be used to select the appropriate treatment for a subjecthaving a particular genotype.

The method for predicting which subjects will respond to a particulartherapeutic agent include administering a therapeutic agent and alabeled moiety to the subject, wherein the labeled moiety isincorporated into alpha-synuclein as it is produced in the subject. Inone embodiment, the therapeutic agent may be administered to the subjectprior to the administration of the labeled moiety. In anotherembodiment, the labeled moiety may be administered to the subject priorto the administration of the therapeutic agent. The period of timebetween the administration of each may be several minutes, an hour,several hours, or many hours. In still another embodiment, thetherapeutic agent and the labeled moiety may be administeredsimultaneously. The method further includes collecting at least onebiological sample, which includes labeled and unlabeled alpha-synuclein,determining a ratio of the labeled alpha-synuclein and unlabeledalpha-synuclein in the sample, and calculating the metabolism ofalpha-synuclein in the subject. Thereafter, a comparison of thecalculated metabolism to a control value will determine whether thetherapeutic agent alters the metabolism (e.g., by altering the rate ofproduction or the rate of clearance) of alpha-synuclein in the subject.

Those of skill in the art will appreciate that the therapeutic agent canand will vary depending upon the neurological or neurodegenerativedisease or disorder to be treated. Non-limiting examples of suitabletherapeutic agents include small molecule inhibitors of alpha-synucleinproduction, humanized antibodies against alpha-synuclein,alpha-synuclein CNS clearance activators, sirtuin 2 inhibitors,proteosome inhibitors, small molecule inhibitors of alpha-synucleinpolymerization.

Other suitable AD therapeutic agents include cholesterylester transferprotein (CETP) inhibitors, metalloprotease inhibitors, cholinesteraseinhibitors, NMDA receptor antagonists, hormones, neuroprotective agents,Aβ production inhibitors such as inhibitors and modulators of gamma andbeta secretases, anti-Aβ antibodies, anti-Tau antibodies, and cell deathinhibitors. Many of the above mentioned therapeutic agents may alsoaffect the in vivo metabolism of other proteins implicated inneurodegenerative disorders.

The therapeutic agent may be administered to the subject in accord withknown methods. Typically, the therapeutic agent will be administeredorally, but other routes of administration such as parenteral or topicalmay also be used. The amount of therapeutic agent that is administeredto the subject can and will vary depending upon the type of agent, thesubject, and the particular mode of administration. Those skilled in theart will appreciate that dosages may be determined with guidance fromGoodman & Goldman's The Pharmacological Basis of Therapeutics, TenthEdition (2001), Appendix II, pp. 475-493, and the Physicians' DeskReference.

In another aspect, the invention provides a kit for performing themethods of the invention. In one embodiment, a kit is provided fordiagnosing and/or monitoring the progression or treatment of aneurological or neurodegenerative disease in a subject. The kit includesone or more labeled moieties (e.g., labeled amino acids) and a means foradministering the one or more amino acids to the subject. The kit mayfurther include a means for obtaining a biological sample at regulartime intervals from the subject. In certain embodiments, the kit willalso include instructions for detecting and determining the ratio oflabeled to unlabeled alpha-synuclein over time and for calculating themetabolism of alpha-synuclein. In one embodiment, the instructions willdisclose methods for comparing the calculated concentration to certainstandards and/or controls as disclosed herein.

In another embodiment, the kit of the invention provides acompartmentalized carrier including one or more containers containingthe labeled moiety and the various means for performing the methods ofthe invention.

In this embodiment of the invention, we demonstrate the feasibility of astable isotope labeling kinetics (SILK) alpha-synuclein assay. FIG. 1shows the tryptic cleavage sites in the alpha-synuclein sequence andthus a list of possible tryptic peptides originating fromalpha-synuclein. Other proteases can be used instead of trypsin and willyield different cleavage patterns and different peptides. When digestingrecombinant alpha-synuclein or alpha-synuclein isolated from biologicalsources we observed several tryptic peptides originating fromalpha-synuclein. FIG. 3 shows a list of peptides that we have observedeither from recombinant alpha-synuclein or from alpha-synuclein that hasbeen isolated from CSF or other biological sources.

The following examples are provided to further illustrate the advantagesand features of the present invention, but are not intended to limit thescope of the invention. While they are typical of those that might beused, other procedures, methodologies, or techniques known to thoseskilled in the art may alternatively be used.

EXAMPLES

The following examples are included to demonstrate preferred embodimentsof the invention. It should be appreciated by those of skill in the artthat the techniques disclosed in the examples that follow representtechniques discovered by the inventors to function well in the practiceof the invention, and thus can be considered to constitute preferredmodes for its practice. However, those of skill in the art should, inlight of the present disclosure, appreciate that many changes can bemade in the specific embodiments which are disclosed and still obtain alike or similar result without departing from the spirit and scope ofthe invention.

Example 1 Measurement of Incorporation of ¹³C₆ Leucine intoAlpha-Synuclein Produced by Cells

Tissue culture cells (SH-SY5Y) were stably transfected with a constructthat leads to over-expression of alpha-synuclein. The cells were grownin media containing known ratios of ¹³C₆ to ¹²C₆ labeled leucine (tracerto tracee ratio; TTR) (TTR=0.00, 0.0127, 0.0256, 0.0526, 0.111, 0.25).Media was collected after 3, 5, and 7 days of growing in the labeledmedia. Alpha-synuclein was isolated from media samples byimmunoprecipitation using C2N-ASMAB3. Isolated proteins were digestedwith trypsin and analyzed on a TSQ-Vantage triple quadruple massspectrometer setup to monitor the labeled and unlabeled alpha-synuclein35-43 peptide. The ratio of labeled to unlabeled alpha-synuclein wascalculated for each sample. The approximate concentration ofalpha-synuclein as measured by the intensity of the labeled andunlabeled alpha-synuclein increased from the initial collection to thesubsequent collections as the cells grew more confluent. In addition,the ratio of labeled to unlabeled alpha-synuclein more closely matchedthe expected concentrations as the cells turned over the originallyunlabeled alpha-synuclein and produced new alpha-synuclein using themixture of labeled and unlabeled amino acids.

Example 2 Measurement of Incorporation of ¹³C₆ Leucine intoAlpha-Synuclein Produced by Humans

A human volunteer was administered ¹³C₆ leucine for 9 hours and had CSFsamples taken every hour for 36 hours starting at the time of leucineinfusion. Alpha-synuclein was isolated from the CSF samples as well assamples from one ¹³C₆ leucine alpha-synuclein standard curve byimmunoprecipitation and digested with trypsin. Incorporation of ¹³C₆leucine into the 35-43 peptide was analyzed for each sample by massspectrometer.

Although the invention has been described with reference to the aboveexamples, it will be understood that modifications and variations areencompassed within the spirit and scope of the invention. Accordingly,the invention is limited only by the following claims.

1. A method to determine the prognosis, diagnosis, efficacy of atherapeutic regimen, or predict subject response to a therapeutic agentto treat an alpha-synuclein related disease or disorder in a subjectcomprising contacting a biological sample from a subject with a labeledmoiety to detect the level of alpha-synuclein in the sample wherein thelevel is compared with a reference standard level, wherein a differencein the level in the sample as compared to the reference level allows oneto determine the prognosis, diagnosis, efficacy of the therapeuticregimen or predict subject response to a therapeutic agent to treat analpha-synuclein related disease or disorder.
 2. The method of claim 1,wherein the diagnosis of an alpha-synuclein related disease or disordercomprises: (a) administration of a labeled moiety to a subject suspectedof having an alpha-synuclein related disease or disorder; (b) collectionof a biological sample from the subject and a corresponding normalsample; (c) measurement of labeled alpha-synuclein and unlabeledalpha-synuclein from the subject and corresponding normal sample; (d)determination of the ratio of labeled alpha-synuclein to unlabeledalpha-synuclein from the subject and corresponding normal sample; (e)determination of alpha-synuclein metabolism from the ratios of step (d);and (f) comparison of the alpha-synuclein metabolism from the subject tothe alpha-synuclein metabolism from the corresponding normal sample;wherein a change in the alpha-synuclein metabolism of the subjectcompared to the corresponding normal sample is indicative of positivediagnosis of an alpha-synuclein related disease or disorder; therebydiagnosing an alpha-synuclein related disease or disorder.
 3. The methodof claim 1, wherein the determination of the prognosis of analpha-synuclein related disease or disorder comprises: (a)administration of a labeled moiety to a subject suspected of having analpha-synuclein related disease or disorder; (b) collection of abiological sample from the subject and a corresponding normal sample;(c) measurement of labeled alpha-synuclein and unlabeled alpha-synucleinfrom the subject and corresponding normal sample; (d) determination ofthe ratio of labeled alpha-synuclein to unlabeled alpha-synuclein fromthe subject and corresponding normal sample; (e) determination ofalpha-synuclein metabolism from the ratios of step (d); and (f)comparison of the alpha-synuclein metabolism from the subject to thealpha-synuclein metabolism from the corresponding normal sample; whereina change in the alpha-synuclein metabolism of the subject compared tothe corresponding normal sample is indicative of positive prognosis ofan alpha-synuclein related disease or disorder; thereby prognosing analpha-synuclein related disease or disorder.
 4. The method of claim 1,wherein the determination of the efficacy of a therapeutic regimen totreat an alpha-synuclein related disease or disorder comprises: (a)administration of a labeled moiety and a therapeutic agent to a subjecthaving an alpha-synuclein related disease or disorder, wherein thetherapeutic agent is selected from the group consisting of: smallmolecule inhibitors of alpha-synuclein, antibodies againstalpha-synuclein, alpha-synuclein clearance activators, sirtuin 2inhibitors, proteomsome inhibitors, small molecule inhibitors ofalpha-synuclein polymerization, L-DOPA, cholesterylester transferprotein (CEPT) inhibitors, metalloprotease inhibitors, cholinesteraseinhibitors, NMDA receptor antagonists, hormones, neuroprotective agentsand cell death inhibitors; (b) collection of a biological sample fromthe subject and a corresponding normal sample; (c) measurement oflabeled alpha-synuclein and unlabeled alpha-synuclein from the subjectand corresponding normal sample; (d) determination of the ratio oflabeled alpha-synuclein to unlabeled alpha-synuclein from the subjectand corresponding normal sample; (e) determination of alpha-synucleinmetabolism from the ratios of step (d); and (f) comparison of thealpha-synuclein metabolism from the subject to the alpha-synucleinmetabolism from the corresponding normal sample; wherein a change in thealpha-synuclein metabolism of the subject compared to the correspondingnormal sample is indicative of efficacy of a therapeutic regimen of atherapeutic agent to treat an alpha-synuclein related disease ordisorder; thereby determining the efficacy of a therapeutic regimen totreat an alpha-synuclein related disease or disorder.
 5. An in vivomethod to identify a therapeutic agent to treat an alpha-synucleinrelated disease or disorder comprising: (a) administration of a labeledmoiety and a therapeutic agent to a subject suspected of having analpha-synuclein related disease or disorder or cells, wherein thetherapeutic agent is selected from the group consisting of: smallmolecule inhibitors of alpha-synuclein, antibodies againstalpha-synuclein, alpha-synuclein clearance activators, sirtuin 2inhibitors, proteomsome inhibitors, small molecule inhibitors ofalpha-synuclein polymerization, L-DOPA, cholesterylester transferprotein (CEPT) inhibitors, metalloprotease inhibitors, cholinesteraseinhibitors, NMDA receptor antagonists, hormones, neuroprotective agentsand cell death inhibitors; (b) collection of a biological sample fromthe subject and a corresponding normal sample or the cells and acorresponding normal samples; (c) measurement of labeled alpha-synucleinand unlabeled alpha-synuclein from the subject and corresponding normalsample; (d) determination of the ratio of labeled alpha-synuclein tounlabeled alpha-synuclein from the subject and corresponding normalsample or the cells and a corresponding normal samples; (e)determination of alpha-synuclein metabolism from the ratios of step (d);and (f) comparison of the alpha-synuclein metabolism from the subject tothe alpha-synuclein metabolism from the corresponding normal sample orthe cells and a corresponding normal samples; wherein a change inalpha-synuclein metabolism of the subject compared to the correspondingnormal sample or a change in alpha-synuclein metabolism of the cellscompared to the corresponding normal sample is indicative of theidentification of a therapeutic agent to treat an alpha-synucleinrelated disease or disorder; thereby identifying a therapeutic agent totreat an alpha-synuclein related disease or disorder an alpha-synucleinrelated disease or disorder.
 6. The method of claim 1 wherein theprediction of subject response to a therapeutic agent to treat analpha-synuclein related disease or disorder comprises: (a)administration of a labeled moiety and a therapeutic agent to a subjectsuspected of having an alpha-synuclein related disease or disorderwherein the therapeutic agent is selected from the group consisting of:small molecule inhibitors of alpha-synuclein, antibodies againstalpha-synuclein, alpha-synuclein clearance activators, sirtuin 2inhibitors, proteomsome inhibitors, small molecule inhibitors ofalpha-synuclein polymerization, L-DOPA, cholesterylester transferprotein (CEPT) inhibitors, metalloprotease inhibitors, cholinesteraseinhibitors, NMDA receptor antagonists, hormones, neuroprotective agentsand cell death inhibitors; (b) collection of a biological sample fromthe subject and a corresponding normal sample; (c) measurement oflabeled alpha-synuclein and unlabeled alpha-synuclein from the subjectand corresponding normal sample; (d) determination of the ratio oflabeled alpha-synuclein to unlabeled alpha-synuclein from the subjectand corresponding normal sample; (e) determination of alpha-synucleinmetabolism from the ratios of step (d); and (f) comparison of thealpha-synuclein metabolism from the subject to the alpha-synucleinmetabolism from the corresponding normal sample; wherein a change in thealpha-synuclein metabolism of the subject compared to the correspondingnormal sample is indicative of the identification of a therapeutic agentto treat an alpha-synuclein related disease or disorder; therebydiagnosing an alpha-synuclein related disease or disorder.
 7. The methodof claim 1, wherein the labeled moiety is a labeled amino acid orlabeled water.
 8. The method of claim 7, wherein the amino acid islabeled with a radioisotope or a non-radio-labeled isotope.
 9. Themethod of claim 8, wherein the non-radio labeled isotope is selectedfrom the group consisting of: 2H, 13C, 15N, 17 or 18O and 33, 34 or 36S.10. The method of claim 7, wherein the amino acid is selected from thegroup consisting of leucine, isoleucine and phenylalanine.
 11. Themethod of claim 10, wherein the labeled amino acid is selected from thegroup consisting of one or more of: 15Nx labeled leucine, wherein x=1-6;13Cx labeled phenylalanine, wherein x=1-9 and 13Cx labeled isoleucine,wherein x=1-6.
 12. The method of claim 1, wherein the labeled moiety isa labeled water.
 13. The method of claim 11, wherein the labeled wateris selected from the group consisting of deuterated water or oxygen 18water.
 14. The method of claim 1, wherein the biological sample isselected from the group consisting of: a bodily fluid or a tissuesample.
 15. The method of claim 14, wherein the bodily fluid is selectedfrom the group consisting of: blood, plasma, blood serum, cerebralspinal fluid (CSF), urine, saliva, perspiration and tears and whereinthe tissue sample is a CNS sample.
 16. The method of claim 15, whereinthe CNS sample is selected from the group consisting of: tissue from theCNS system, brain tissue, the forebrain tissue, the interbrain tissue,the midbrain tissue, the hindbrain tissue and the spinal cord tissue.17. A kit for determination of prognosis, diagnosis or efficacy of atherapeutic regimen in a subject having or suspected of having analpha-synuclein related disease or disorder comprising one or morelabeled moieties and a means for administering the one or more moietiesto a subject, a means for obtaining a biological sample and instructionsfor determining the ratio of labeled to unlabeled alpha-synuclein.